This invention relates to a process for producing L-arabinose, enzyme-treated products containing L-arabinose and a process for producing the same, and diet foods, diabetic foods and fruit or vegetable juices with the use of the same, and processes for the production thereof.
L-Arabinose is a non-caloric sweetener which has taste characteristics similar to sucrose and shows little absorbability. It is also known that L-arabinose inhibits enzymes which hydrolyze dissacharides such as sucrose and thus exerts an effect of suppressing an increase in blood glucose level due to the intake of sucrose. Using these characteristics of L-arabinose, there have been known body fat accumulation inhibitors (JP-A-7-309765, JP-A-7-242551), preventives and remedies for diseases related tohyperglycemia (JP-A-6-65080), diet sweeteners and preventives for obesity (JP-X-6-812057) and pet foods (JP-A-2-299555) each containing L-arabinose (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d and xe2x80x9cJP-Xxe2x80x9d as used herein means a publication of Japanese translation of a PCT patent application). Also, L-arabinose is a saccharide which is useful as a starting material for synthesizing drugs.
L-Arabinose occurs as arabinan, arabinoxylan, arabinogalactan and the like in hemicellulose of higher plants. Also, a trace amount of L-arabinose in a free state is contained in fermented foods such as miso and sake, instant coffee, etc. Thus, L-arabinose is a saccharide which has been commonly taken over a long time.
It has been a practice to produce L-arabinose by alkali-extracting hemicellulose contained in corn fiber, gum arabic, beet pulp, etc., followed by acidolysis (JP-A-11-313700, JP-A-11-113600).
However, these acidolysis methods cannot be regarded as satisfactory, since these methods suffer from some problems such that carcinogens unsuitable for food and drug materials are likely formed, a special reaction apparatus should be employed in the acid treatment performed at 100xc2x0 C. or higher, and a large amount of a salt is formed in the step of neutralization and thus a troublesome post-treatment is needed. Moreover, a troublesome procedure and a high cost are needed in the alkali-extraction of various hemicelluloses from natural substances. Further, there arises an additional problem such as the disposal method and spot of the waste remaining after the acquisition of L-arabinose while taking the effects thereof on the environment into consideration.
It is proposed to produce L-arabinose by treating beet pulp employed as the starting material with an alkali under heating followed by precipitation with ethanol, then acidolyzing or treating with an enzyme the thus extracted arabinan (JP-A-9-299093; J. Soc. of Agr. Chem., vol. 49 (6), pp.295-305, 1975). However, this method suffers from a problem that a troublesome procedure is required in the extraction of arabinan from the starting natural substance. Therefore, this method has been considered as little applicable to the industrial and economical production of L-arabinose because of the extremely low yield of L-arabinose established thereby.
In the report of Spagnuolo et al. (Biotechnology and Bioengineering, vol. 64(6), pp.685-691, 1999), L-arabinose could be obtained at a high yield. However, this method is unsuitable for the mass production of L-arabinose, since a deproteinization treatment of treating beet pulp with a protease and filtering, and an autoclaving treatment (121xc2x0 C., 20 minutes) are needed as pretreatments in this method, which makes the procedure complicated.
On the other hand, conventional diet foods involve products containing konnyaku, etc. which give a feeling of fullness and yet have low caloric values, products containing low caloric sweeteners as a substitute for sugar, and products containing drugs having anorexic or sweetness-repellent effects.
However, there is no sweetener superior in taste characteristics to sugar. Use of less digestive components which merely give a feeling of fullness (konnyaku, etc.) or addition of drugs having the above-described effects, etc. cannot be considered as a favorable means of providing pleasant eating habits.
Many of conventional diabetic foods for regulating total calorie intake are unappetizing. Although calorie intake can be easily controlled in the hospital, preparation of calorie-restricted foods, injection of insulin for inhibiting an increase in blood glucose level and intake of drugs impose serious burden and stress both in mind and body of patients after discharge from the hospital.
Conventional juices, which are obtained by pressing fruits, etc., contain little L-arabinose as a monosaccharide. On the other hand, press juice cakes obtained in the production of juices are rich in L-arabinose in the form of polysaccharides. Although only a portion thereof is utilized as feeds and the like, they are mostly dumped as waste. That is to say, L-arabinose remaining therein is not effectively utilized at the present stage.
Although some of the conventional juices contain ground fruits, etc. or small pieces thereof, these juices merely containing ground fruits, etc. or small pieces thereof contain only an extremely small amount of L-arabinose as a monosaccharide. The polysaccharides such as arabinan, arabinoxylan or arabinogalactan, which are contained in a large amount in the ground fruits, etc. or small pieces thereof, are not degraded into L-arabinose in the human large intestine but mostly excreted. Therefore, it is considered that these products contain almost no additional component other than fiber from a nutritional viewpoint, though they are improved in the eating quality, i.e., feeling in the mouth, touch to the tongue, etc.
Although L-arabinose has valuable functions, the conventional processes for producing L-arabinose cost a great deal as described above and thus the practical utilization of L-arabinose as a starting material for foods, drugs, etc. is disturbed thereby. An object of the invention is to provide a process for economically producing L-arabinose and enzyme-treated products containing L-arabinose obtained from natural substances containing arabinan, arabinoxylan or arabinogalactan and a process for producing the same.
Although L-arabinose is sufficiently usable as a low caloric component to be employed in diet foods or diabetic foods, its content in foods should have been restricted due to the high cost caused by the troublesome handling procedures in the conventional processes for producing it. As a result, it is difficult to fully utilize the functions of L-arabinose.
Although dietary fiber inherently has sufficient functions, it has been employed hitherto almost exclusively for ameliorating intestinal disorders. Thus, it is not sufficiently expected as exerting the diet effect. In case of using as a material for diabetic foods, moreover, it is feared that dietary fiber would fail to achieve the effect of controlling the blood glucose level.
Another object of the invention is to provide diet foods or diabetic foods which have enhanced functions of L-arabinose to thereby make it possible to reduce the content of L-arabinose in foods and also posses the functions of dietary fiber, and a process for economically and conveniently producing the same.
Another object of the invention is to provide fruit or vegetable juices containing L-arabinose having functions such as an effect of inhibiting an increase in the blood glucose level, which is considered to be achieved by the effect of L-arabinose of inhibiting disaccharide-hydrolyzing enzymes, imparted thereto by adding an L-arabinose-containing press juice cake or a solution obtained by solid/liquid separation thereof to conventional juices.
In order to achieve these objects, the inventors have conducted extensive studies. As a result, they have found out that L-arabinose can be economically produced by treating a natural material containing arabinan, arabinoxylan or arabinogalactan directly with an enzyme having an activity of acting on natural substances containing arabinan, arabinoxylan or arabinogalactan and thus releasing L-arabinose without separating or extracting arabinan, arabinoxylan or arabinogalactan from the natural substance containing arabinan, arabinoxylan or arabinogalactan.
They have further found out that the effect of inhibiting an increase in blood glucose level after meal can be enhanced by adding dietary fiber together with L-arabinose to foods. They have furthermore found out that dietary fiber can be obtained together with L-arabinose by treating a dietary fiber material originating in a natural substance containing arabinan, arabinoxylan or arabinogalactan with a specific enzyme.
Moreover, they have found out that juices containing L-arabinose can be produced by treating press juice cake directly with an enzyme having an activity of acting on natural substances containing arabinan, arabinoxylan or arabinogalactan and thus releasing L-arabinose to give L-arabinose-containing press juice cake and then adding it, either as such or as an L-arabinose-containing fraction obtained after pressing, to juices.
The invention has been thus completed. Namely, the gist of the first embodiment of the invention resides in a process for producing L-arabinose by treating a natural material containing arabinan, arabinoxylan or arabinogalactan with an enzyme having an activity of acting on natural substances containing arabinan, arabinoxylan or arabinogalactan and thus releasing L-arabinose to give L-arabinose, characterized in that the above-described natural substance is directly treated with the above-described enzyme without separating or extracting arabinan, arabinoxylan or arabinogalactan. The gist of the second embodiment of the invention resides in an enzyme-treated product containing L-arabinose characterized in that a natural substance containing arabinan, arabinoxylan or arabinogalactan contains L-arabinose. The gist of the third embodiment of the invention resides in a process for producing an enzyme-treated product containing L-arabinose characterized by comprising releasing L-arabinose by treating a natural substance containing arabinan, arabinoxylan or arabinogalactan directly with an enzyme having an activity of acting on natural substances containing arabinan, arabinoxylan or arabinogalactan and thus releasing L-arabinose to give the enzyme-treated product containing L-arabinose as described above.
The gist of the fourth embodiment of the invention resides in a diet food characterized by containing L-arabinose and dietary fiber wherein it is preferable that the L-arabinose and dietary fiber employed are obtained by treating a dietary fiber material originating in a natural substance containing arabinan, arabinoxylan or arabinogalactan with an enzyme. The gist of the fifth embodiment of the invention resides in a process for producing a diet food characterized by comprising treating a dietary fiber material originating in a natural substance containing arabinan, arabinoxylan or arabinogalactan with an enzyme which degrades arabinan, arabinoxylan or arabinogalactan to give an enzyme-treated product containing L-arabinose and dietary fiber and adding the thus obtained enzyme-treated product to a food.
The gist of the sixth embodiment of the invention resides in a diabetic food characterized by containing L-arabinose and dietary fiber wherein it is preferable that the L-arabinose and dietary fiber employed are obtained by treating a dietary fiber material originating in a natural substance containing arabinan, arabinoxylan or arabinogalactan with an enzyme. The gist of the seventh embodiment of the invention resides in a process for producing a diabetic food characterized by comprising treating a dietary fiber material originating in a natural substance containing arabinan, arabinoxylan or arabinogalactan with an enzyme which degrades arabinan, arabinoxylan or arabinogalactan to give an enzyme-treated product containing L-arabinose and dietary fiber and adding the thus obtained enzyme-treated product to a food.
The gist of the eighth embodiment of the invention resides in an L-arabinose-containing fruit or vegetable juice characterized by containing an L-arabinose-containing fraction obtained by treating a fruit or vegetable press cake containing arabinan, arabinoxylan or arabinogalactan with an enzyme. The gist of the ninth embodiment of the invention resides in a process for producing an arabinose-containing fruit or vegetable juice characterized by comprising treating a fruit or a vegetable containing arabinan, arabinoxylan or arabinogalactan to divide into a juice and a press juice cake, treating the press juice cake with an enzyme to release L-arabinose and then adding the fraction containing the released L-arabinose to the juice.